server: ignore invalid range handers instead of throwing

lib/server.js

@@ -112,18 +112,23 @@ function Server (torrent, opts) {
         'DLNA.ORG_OP=01;DLNA.ORG_CI=0;DLNA.ORG_FLAGS=01700000000000000000000000000000'
       )
 
-      var range
-      if (req.headers.range) {
+      // `rangeParser` returns an array of ranges, or an error code (number) if
+      // there was an error parsing the range.
+      var range = rangeParser(file.length, req.headers.range || '')
+
+      if (Array.isArray(range)) {
+        // no support for multi-range request, just use the first range
+        range = range[0]
+
         res.statusCode = 206
-        // no support for multi-range reqs
-        range = rangeParser(file.length, req.headers.range)[0]
         debug('range %s', JSON.stringify(range))
         res.setHeader(
           'Content-Range',
           'bytes ' + range.start + '-' + range.end + '/' + file.length
         )
         res.setHeader('Content-Length', range.end - range.start + 1)
       } else {
+        range = null
         res.setHeader('Content-Length', file.length)
       }